Operators are facing a rapid increase in traffic of data traffic flows. However, operators can provide limited bandwidth resources, and how to use limited bandwidth to provide a service for traffic that increases rapidly becomes an urgent problem to be resolved by the operators.
Currently, a flow mobility method based on the Proxy Mobile IP (PMIP for short)/GPRS tunneling protocol (GTP for short) is being made. In the flow mobility method based on the GTP/PMIP, different traffic flows on a same packet data network (PDN for short) connection may be separately transmitted between a 3rd Generation Partnership Project (3GPP for short) 3GPP network and a non-3GPP network, and a same traffic flow may be switched between the 3GPP network and the non-3GPP network. Specifically, the 3GPP standard protocol supports user equipment (UE for short) in simultaneously accessing a 3GPP network and a non-3GPP network. In addition, the UE may simultaneously access a same PDN connection by using the 3GPP network and the non-3GPP network, that is, different data flows on a same PDN connection may be distributed in a 3GPP system and a non-3GPP system and transmitted separately. For example, if the UE has both a video service and a voice service on a same PDN connection, the video service may be transmitted by using the non-3GPP network, and the voice service may be transmitted by using the 3GPP network. In comparison with a case in which both the video service and the voice service are transmitted in the 3GPP network or the non-3GPP network, bandwidth of the video service and the voice service can be increased, and network resource utilization can be improved.
However, in the prior art, data packets in a same traffic flow can be transmitted only in one access network, that is, a same traffic flow is transmitted in either the 3GPP network or the non-3GPP network. When the UE has only one traffic flow, bandwidth of the UE cannot be increased. In addition, when a traffic flow is switched between the two networks, multiple pieces of signaling are exchanged between the UE and a network side. Consequently, a traffic flow switching time is delayed.